I have had 3 .91 FX and everyone was a terrific performer. While Great Planes recommends either 13X8 or 13X9, this engine will pull a 15X6 with great authority.

If you take time to properly breakin the engine it will serve you well. It is an easy starter with great transition and pulling power.

My current one is in a U Can-Do 3D and it is well overpowered.